diff --git a/src/cryptonote_core/cryptonote_basic.h b/src/cryptonote_core/cryptonote_basic.h
index afe785eb..e5a5cc6f 100644
--- a/src/cryptonote_core/cryptonote_basic.h
+++ b/src/cryptonote_core/cryptonote_basic.h
@@ -180,7 +180,7 @@ namespace cryptonote
       FIELD(extra)
     END_SERIALIZE()
 
-  protected:
+  public:
     transaction_prefix(){}
   };
 
diff --git a/src/cryptonote_core/cryptonote_boost_serialization.h b/src/cryptonote_core/cryptonote_boost_serialization.h
index f222db94..41f86480 100644
--- a/src/cryptonote_core/cryptonote_boost_serialization.h
+++ b/src/cryptonote_core/cryptonote_boost_serialization.h
@@ -143,6 +143,16 @@ namespace boost
   }
 
 
+  template <class Archive>
+  inline void serialize(Archive &a, cryptonote::transaction_prefix &x, const boost::serialization::version_type ver)
+  {
+    a & x.version;
+    a & x.unlock_time;
+    a & x.vin;
+    a & x.vout;
+    a & x.extra;
+  }
+
   template <class Archive>
   inline void serialize(Archive &a, cryptonote::transaction &x, const boost::serialization::version_type ver)
   {
diff --git a/src/cryptonote_core/cryptonote_format_utils.cpp b/src/cryptonote_core/cryptonote_format_utils.cpp
index ee9a0080..ddcab4f0 100644
--- a/src/cryptonote_core/cryptonote_format_utils.cpp
+++ b/src/cryptonote_core/cryptonote_format_utils.cpp
@@ -321,6 +321,11 @@ namespace cryptonote
     return pub_key_field.pub_key;
   }
   //---------------------------------------------------------------
+  crypto::public_key get_tx_pub_key_from_extra(const transaction_prefix& tx_prefix)
+  {
+    return get_tx_pub_key_from_extra(tx_prefix.extra);
+  }
+  //---------------------------------------------------------------
   crypto::public_key get_tx_pub_key_from_extra(const transaction& tx)
   {
     return get_tx_pub_key_from_extra(tx.extra);
diff --git a/src/cryptonote_core/cryptonote_format_utils.h b/src/cryptonote_core/cryptonote_format_utils.h
index 6dac8e88..e0ffbed6 100644
--- a/src/cryptonote_core/cryptonote_format_utils.h
+++ b/src/cryptonote_core/cryptonote_format_utils.h
@@ -89,6 +89,7 @@ namespace cryptonote
 
   bool parse_tx_extra(const std::vector<uint8_t>& tx_extra, std::vector<tx_extra_field>& tx_extra_fields);
   crypto::public_key get_tx_pub_key_from_extra(const std::vector<uint8_t>& tx_extra);
+  crypto::public_key get_tx_pub_key_from_extra(const transaction_prefix& tx);
   crypto::public_key get_tx_pub_key_from_extra(const transaction& tx);
   bool add_tx_pub_key_to_extra(transaction& tx, const crypto::public_key& tx_pub_key);
   bool add_extra_nonce_to_tx_extra(std::vector<uint8_t>& tx_extra, const blobdata& extra_nonce);
diff --git a/src/simplewallet/simplewallet.cpp b/src/simplewallet/simplewallet.cpp
index 35469226..9e734145 100644
--- a/src/simplewallet/simplewallet.cpp
+++ b/src/simplewallet/simplewallet.cpp
@@ -2068,7 +2068,7 @@ bool simple_wallet::show_incoming_transfers(const std::vector<std::string>& args
         (m_wallet->is_transfer_unlocked(td) ? tr("unlocked") : tr("locked")) %
         (td.is_rct() ? tr("RingCT") : tr("-")) %
         td.m_global_output_index %
-        get_transaction_hash (td.m_tx);
+        td.m_txid;
     }
   }
 
diff --git a/src/wallet/api/transaction_history.cpp b/src/wallet/api/transaction_history.cpp
index db42e214..95aafb04 100644
--- a/src/wallet/api/transaction_history.cpp
+++ b/src/wallet/api/transaction_history.cpp
@@ -165,9 +165,8 @@ void TransactionHistoryImpl::refresh()
     for (std::list<std::pair<crypto::hash, tools::wallet2::unconfirmed_transfer_details>>::const_iterator i = upayments.begin(); i != upayments.end(); ++i) {
         const tools::wallet2::unconfirmed_transfer_details &pd = i->second;
         const crypto::hash &hash = i->first;
-        uint64_t amount = 0;
-        cryptonote::get_inputs_money_amount(pd.m_tx, amount);
-        uint64_t fee = amount - get_outs_money_amount(pd.m_tx);
+        uint64_t amount = pd.m_amount_in;
+        uint64_t fee = amount - pd.m_amount_out;
         std::string payment_id = string_tools::pod_to_hex(i->second.m_payment_id);
         if (payment_id.substr(16).find_first_not_of('0') == std::string::npos)
             payment_id = payment_id.substr(0,16);
diff --git a/src/wallet/wallet2.cpp b/src/wallet/wallet2.cpp
index 4e014462..5d51efc1 100644
--- a/src/wallet/wallet2.cpp
+++ b/src/wallet/wallet2.cpp
@@ -225,6 +225,24 @@ static uint64_t decodeRct(const rct::rctSig & rv, const rct::key & sk, unsigned
 //----------------------------------------------------------------------------------------------------
 void wallet2::process_new_transaction(const cryptonote::transaction& tx, const std::vector<uint64_t> &o_indices, uint64_t height, uint64_t ts, bool miner_tx, bool pool)
 {
+  class lazy_txid_getter
+  {
+    const cryptonote::transaction &tx;
+    crypto::hash lazy_txid;
+    bool computed;
+    public:
+    lazy_txid_getter(const transaction &tx): tx(tx), computed(false) {}
+    const crypto::hash &operator()()
+    {
+      if (!computed)
+      {
+        lazy_txid = cryptonote::get_transaction_hash(tx);
+        computed = true;
+      }
+      return lazy_txid;
+    }
+  } txid(tx);
+
   if (!miner_tx)
     process_unconfirmed(tx, height);
   std::vector<size_t> outs;
@@ -235,7 +253,7 @@ void wallet2::process_new_transaction(const cryptonote::transaction& tx, const s
   if(!parse_tx_extra(tx.extra, tx_extra_fields))
   {
     // Extra may only be partially parsed, it's OK if tx_extra_fields contains public key
-    LOG_PRINT_L0("Transaction extra has unsupported format: " << get_transaction_hash(tx));
+    LOG_PRINT_L0("Transaction extra has unsupported format: " << txid());
   }
 
   // Don't try to extract tx public key if tx has no ouputs
@@ -244,7 +262,7 @@ void wallet2::process_new_transaction(const cryptonote::transaction& tx, const s
     tx_extra_pub_key pub_key_field;
     if(!find_tx_extra_field_by_type(tx_extra_fields, pub_key_field))
     {
-      LOG_PRINT_L0("Public key wasn't found in the transaction extra. Skipping transaction " << get_transaction_hash(tx));
+      LOG_PRINT_L0("Public key wasn't found in the transaction extra. Skipping transaction " << txid());
       if(0 != m_callback)
 	m_callback->on_skip_transaction(height, tx);
       return;
@@ -452,7 +470,8 @@ void wallet2::process_new_transaction(const cryptonote::transaction& tx, const s
 	    td.m_block_height = height;
 	    td.m_internal_output_index = o;
 	    td.m_global_output_index = o_indices[o];
-	    td.m_tx = tx;
+	    td.m_tx = (const cryptonote::transaction_prefix&)tx;
+	    td.m_txid = txid();
             td.m_key_image = ki[o];
             td.m_amount = tx.vout[o].amount;
             if (td.m_amount == 0)
@@ -466,9 +485,9 @@ void wallet2::process_new_transaction(const cryptonote::transaction& tx, const s
             }
 	    set_unspent(td);
 	    m_key_images[td.m_key_image] = m_transfers.size()-1;
-	    LOG_PRINT_L0("Received money: " << print_money(td.amount()) << ", with tx: " << get_transaction_hash(tx));
+	    LOG_PRINT_L0("Received money: " << print_money(td.amount()) << ", with tx: " << txid());
 	    if (0 != m_callback)
-	      m_callback->on_money_received(height, td.m_tx, td.m_amount);
+	      m_callback->on_money_received(height, tx, td.m_amount);
           }
         }
 	else if (m_transfers[kit->second].m_spent || m_transfers[kit->second].amount() >= tx.vout[o].amount)
@@ -492,7 +511,8 @@ void wallet2::process_new_transaction(const cryptonote::transaction& tx, const s
 	    td.m_block_height = height;
 	    td.m_internal_output_index = o;
 	    td.m_global_output_index = o_indices[o];
-	    td.m_tx = tx;
+	    td.m_tx = (const cryptonote::transaction_prefix&)tx;
+	    td.m_txid = txid();
             td.m_amount = tx.vout[o].amount;
             if (td.m_amount == 0)
             {
@@ -506,9 +526,9 @@ void wallet2::process_new_transaction(const cryptonote::transaction& tx, const s
             THROW_WALLET_EXCEPTION_IF(td.m_key_image != ki[o], error::wallet_internal_error, "Inconsistent key images");
 	    THROW_WALLET_EXCEPTION_IF(td.m_spent, error::wallet_internal_error, "Inconsistent spent status");
 
-	    LOG_PRINT_L0("Received money: " << print_money(td.amount()) << ", with tx: " << get_transaction_hash(tx));
+	    LOG_PRINT_L0("Received money: " << print_money(td.amount()) << ", with tx: " << txid());
 	    if (0 != m_callback)
-	      m_callback->on_money_received(height, td.m_tx, td.m_amount);
+	      m_callback->on_money_received(height, tx, td.m_amount);
           }
         }
       }
@@ -533,11 +553,11 @@ void wallet2::process_new_transaction(const cryptonote::transaction& tx, const s
             std::string(", expected ") + print_money(td.amount()));
       }
       amount = td.amount();
-      LOG_PRINT_L0("Spent money: " << print_money(amount) << ", with tx: " << get_transaction_hash(tx));
+      LOG_PRINT_L0("Spent money: " << print_money(amount) << ", with tx: " << txid());
       tx_money_spent_in_ins += amount;
       set_spent(td, height);
       if (0 != m_callback)
-        m_callback->on_money_spent(height, td.m_tx, amount, tx);
+        m_callback->on_money_spent(height, tx, amount, tx);
     }
   }
 
@@ -589,7 +609,7 @@ void wallet2::process_new_transaction(const cryptonote::transaction& tx, const s
     }
 
     payment_details payment;
-    payment.m_tx_hash      = cryptonote::get_transaction_hash(tx);
+    payment.m_tx_hash      = txid();
     payment.m_amount       = received;
     payment.m_block_height = height;
     payment.m_unlock_time  = tx.unlock_time;
@@ -604,6 +624,9 @@ void wallet2::process_new_transaction(const cryptonote::transaction& tx, const s
 //----------------------------------------------------------------------------------------------------
 void wallet2::process_unconfirmed(const cryptonote::transaction& tx, uint64_t height)
 {
+  if (m_unconfirmed_txs.empty())
+    return;
+
   crypto::hash txid = get_transaction_hash(tx);
   auto unconf_it = m_unconfirmed_txs.find(txid);
   if(unconf_it != m_unconfirmed_txs.end()) {
@@ -915,7 +938,7 @@ void wallet2::update_pool_state()
   std::unordered_map<crypto::hash, wallet2::unconfirmed_transfer_details>::iterator it = m_unconfirmed_txs.begin();
   while (it != m_unconfirmed_txs.end())
   {
-    const std::string txid = epee::string_tools::pod_to_hex(cryptonote::get_transaction_hash(it->second.m_tx));
+    const std::string txid = epee::string_tools::pod_to_hex(it->first);
     bool found = false;
     for (auto it2: res.transactions)
     {
@@ -1141,7 +1164,7 @@ void wallet2::refresh(uint64_t start_height, uint64_t & blocks_fetched, bool& re
   blocks_fetched = 0;
   uint64_t added_blocks = 0;
   size_t try_count = 0;
-  crypto::hash last_tx_hash_id = m_transfers.size() ? get_transaction_hash(m_transfers.back().m_tx) : null_hash;
+  crypto::hash last_tx_hash_id = m_transfers.size() ? m_transfers.back().m_txid : null_hash;
   std::list<crypto::hash> short_chain_history;
   boost::thread pull_thread;
   uint64_t blocks_start_height;
@@ -1213,7 +1236,7 @@ void wallet2::refresh(uint64_t start_height, uint64_t & blocks_fetched, bool& re
       }
     }
   }
-  if(last_tx_hash_id != (m_transfers.size() ? get_transaction_hash(m_transfers.back().m_tx) : null_hash))
+  if(last_tx_hash_id != (m_transfers.size() ? m_transfers.back().m_txid : null_hash))
     received_money = true;
 
   try
@@ -2179,11 +2202,9 @@ float wallet2::get_output_relatedness(const transfer_details &td0, const transfe
 {
   int dh;
 
-#if 0
   // expensive test, and same tx will fall onto the same block height below
-  if (get_transaction_hash(td0.m_tx) == get_transaction_hash(td1.m_tx))
+  if (td0.m_txid == td1.m_txid)
     return 1.0f;
-#endif
 
   // same block height -> possibly tx burst, or same tx (since above is disabled)
   dh = td0.m_block_height > td1.m_block_height ? td0.m_block_height - td1.m_block_height : td1.m_block_height - td0.m_block_height;
@@ -2269,7 +2290,7 @@ void wallet2::add_unconfirmed_tx(const cryptonote::transaction& tx, uint64_t amo
     utd.m_amount_out += d.amount;
   utd.m_change = change_amount;
   utd.m_sent_time = time(NULL);
-  utd.m_tx = tx;
+  utd.m_tx = (const cryptonote::transaction_prefix&)tx;
   utd.m_dests = dests;
   utd.m_payment_id = payment_id;
   utd.m_state = wallet2::unconfirmed_transfer_details::pending;
diff --git a/src/wallet/wallet2.h b/src/wallet/wallet2.h
index 4c361df8..488902d5 100644
--- a/src/wallet/wallet2.h
+++ b/src/wallet/wallet2.h
@@ -99,7 +99,8 @@ namespace tools
     struct transfer_details
     {
       uint64_t m_block_height;
-      cryptonote::transaction m_tx;
+      cryptonote::transaction_prefix m_tx;
+      crypto::hash m_txid;
       size_t m_internal_output_index;
       uint64_t m_global_output_index;
       bool m_spent;
@@ -123,7 +124,7 @@ namespace tools
 
     struct unconfirmed_transfer_details
     {
-      cryptonote::transaction m_tx;
+      cryptonote::transaction_prefix m_tx;
       uint64_t m_amount_in;
       uint64_t m_amount_out;
       uint64_t m_change;
@@ -502,9 +503,9 @@ namespace tools
   };
 }
 BOOST_CLASS_VERSION(tools::wallet2, 14)
-BOOST_CLASS_VERSION(tools::wallet2::transfer_details, 2)
+BOOST_CLASS_VERSION(tools::wallet2::transfer_details, 3)
 BOOST_CLASS_VERSION(tools::wallet2::payment_details, 1)
-BOOST_CLASS_VERSION(tools::wallet2::unconfirmed_transfer_details, 4)
+BOOST_CLASS_VERSION(tools::wallet2::unconfirmed_transfer_details, 5)
 BOOST_CLASS_VERSION(tools::wallet2::confirmed_transfer_details, 2)
 
 namespace boost
@@ -535,7 +536,17 @@ namespace boost
       a & x.m_block_height;
       a & x.m_global_output_index;
       a & x.m_internal_output_index;
-      a & x.m_tx;
+      if (ver < 3)
+      {
+        cryptonote::transaction tx;
+        a & tx;
+        x.m_tx = (const cryptonote::transaction_prefix&)tx;
+        x.m_txid = cryptonote::get_transaction_hash(tx);
+      }
+      else
+      {
+        a & x.m_tx;
+      }
       a & x.m_spent;
       a & x.m_key_image;
       if (ver < 1)
@@ -552,6 +563,9 @@ namespace boost
         return;
       }
       a & x.m_spent_height;
+      if (ver < 3)
+        return;
+      a & x.m_txid;
     }
 
     template <class Archive>
@@ -559,7 +573,16 @@ namespace boost
     {
       a & x.m_change;
       a & x.m_sent_time;
-      a & x.m_tx;
+      if (ver < 5)
+      {
+        cryptonote::transaction tx;
+        a & tx;
+        x.m_tx = (const cryptonote::transaction_prefix&)tx;
+      }
+      else
+      {
+        a & x.m_tx;
+      }
       if (ver < 1)
         return;
       a & x.m_dests;
diff --git a/src/wallet/wallet_rpc_server.cpp b/src/wallet/wallet_rpc_server.cpp
index 20a9ebe9..1786b776 100644
--- a/src/wallet/wallet_rpc_server.cpp
+++ b/src/wallet/wallet_rpc_server.cpp
@@ -729,7 +729,7 @@ namespace tools
         rpc_transfers.amount       = td.amount();
         rpc_transfers.spent        = td.m_spent;
         rpc_transfers.global_index = td.m_global_output_index;
-        rpc_transfers.tx_hash      = epee::string_tools::pod_to_hex(cryptonote::get_transaction_hash(td.m_tx));
+        rpc_transfers.tx_hash      = epee::string_tools::pod_to_hex(td.m_txid);
         rpc_transfers.tx_size      = txBlob.size();
         res.transfers.push_back(rpc_transfers);
       }
diff --git a/tests/functional_tests/transactions_flow_test.cpp b/tests/functional_tests/transactions_flow_test.cpp
index 6bf91010..58532834 100644
--- a/tests/functional_tests/transactions_flow_test.cpp
+++ b/tests/functional_tests/transactions_flow_test.cpp
@@ -281,7 +281,7 @@ bool transactions_flow_test(std::string& working_folder,
     w2.get_transfers(tc);
     BOOST_FOREACH(tools::wallet2::transfer_details& td, tc)
     {
-      auto it = txs.find(get_transaction_hash(td.m_tx));
+      auto it = txs.find(td.m_txid);
       CHECK_AND_ASSERT_MES(it != txs.end(), false, "transaction not found in local cache");
       it->second.m_received_count += 1;
     }
diff --git a/tests/unit_tests/output_selection.cpp b/tests/unit_tests/output_selection.cpp
index a3164fa4..4344d1ff 100644
--- a/tests/unit_tests/output_selection.cpp
+++ b/tests/unit_tests/output_selection.cpp
@@ -42,6 +42,11 @@ static tools::wallet2::transfer_container make_transfers_container(size_t N)
     tools::wallet2::transfer_details &td = transfers.back();
     td.m_block_height = 1000;
     td.m_spent = false;
+    td.m_txid = cryptonote::null_hash;
+    td.m_txid.data[0] = n & 0xff;
+    td.m_txid.data[1] = (n >> 8) & 0xff;
+    td.m_txid.data[2] = (n >> 16) & 0xff;
+    td.m_txid.data[3] = (n >> 24) & 0xff;
   }
   return transfers;
 }